Name: Class: Exam 4--PHYS 101--Fall 2018 Multiple Choice Identify the choice that best completes the statement or answers the question. 1. The answer to this question is B. a. A b. B c. C d. D 5. A ferris wheel with a radius of 20.0 m rotates at a speed of 1.00 rev/min (=0.10 rad/s). A person with a mass of 100.0 kg sits in a chair. As the ferris wheel spins, the person is at the lowest point. What is the normal force acting on the person? 2. How many revolutions is 400 degrees? a. 2500 rev b. 64 rev c. 1.1 rev d. 144,000 rev 3. What is the angular displacement of a clock s hour hand, in radians, between Noon and 6pm? π a. 2 b. 2π 3π c. 2 d. π a. 1200 N b. 3000 N c. 980 N d. 1020 N e. 1000 N 6. A fan spins at 12.0 rev/s. You turn it off, and it slows at 3.0 rev/s 2. What is its angular displacement before coming to rest? 4. A car rounds a curve on a flat road. The coefficient of static friction between the road and tires is 0.70. If the curve has a radius of 50. meters, what is the maximum safe speed at which the car can round the curve? a. 72 rev b. 36 rev c. 48 rev d. 24 rev e. 32 rev a. 71 m/s b. 340 m/s c. 35 m/s d. 19 m/s 1
7. Consider two pits on a CD, one close to the center and one close to the outer edge. When the CD makes one full rotation, which pit would have gone through a greater angle of rotation? Which one would have covered a greater arc length? a. The one close to the center would go through the greater angle of rotation. The one near the outer edge would trace a greater arc length. b. The one close to the center would go through the greater angle of rotation. The one near the center would trace a greater arc length. c. Both would go through the same angle of rotation. The one near the outer edge would trace a greater arc length. d. Both would go through the same angle of rotation. The one near the center would trace a greater arc length. 8. A hoop has a radius of 2.0 meters and a mass of 10.0 kg. The hoop rolls at a speed of 4.0 m/s. What is the total energy of this rolling hoop? 10. These objects have identical dimensions and mass, but they rotate about different axes of rotation, shown with the dotted line. Rank them in order from least to greatest moment of inertia a. B<C<D<A b. D<C=B<A c. B=C<D<A d. C<B<A<D e. B=C<A<D 11. A merry go round has a moment of inertia of 200.0 kg m 2 and a radius of 1.0 m. A 50.0 kg kid jumps onto the edge of the merry-go-round. What is moment of inertia of the system now? a. 160 J b. 40 J c. 80 J d. 120 J 9. A figure skater pulls her arms in to decrease her moment of inertia by a factor of two. As a result, she spins twice as fast. What has happened to her rotational energy? a. it has increased by a factor of 4 b. it has increased by a factor of 2 c. it remains the same d. it has decreased by a factor of 2 e. it has decreased by a factor of 4 a. 250 kg m 2 b. 225 kg m 2 c. 200 kg m 2 d. 175 kg m 2 e. 150 kg m 2 12. Buckets are spinning horizontally on frictionless bearings. Suddenly, it starts raining. Which of these statements is true: a. the buckets moment of inertia will increase, causing the buckets angular momentum to increase b. the buckets will spin at the same angular speed because there is no torque acting on this c. the buckets angular speed will decrease because their moment of inertia is increasing d. None of these are true 2
13. An object has a moment of inertia of 10.0 kg m 2 and is rotating at 6.0 rev/s. The object expands, so the moment of inertia increases to 20.0 kg m 2. What is its new angular speed? 16. Consider the bar in this figure. What is the net torque? a. 1.5 rev/s b. 24 rev/s c. 6.0 rev/s d. 3.0 rev/s e. 12 rev/s 14. You use a class I lever to lift an object of mass 12 kg as in this figure. The distance from the axis of rotation to the object is 3.0 m; the distance from the axis of rotation to where the force is applied is 1.0 m. What minimum force must be applied to lift the object? a. 30 N b. 120 N c. 40 N d. 80 N e. 360 N a. 64 Nm clockwise b. 30 Nm clockwise c. 6 Nm clockwise d. 60 Nm clockwise e. 40 Nm clockwise 17. Consider the bar in the figure from the previous problem; it is initially at rest. After three seconds, what is the angular speed of the bar? a. 120 rad/s b. 20 rad/s c. 30 rad/s d. 80 rad/s e. 40 rad/s 15. A force is applied 3m away from the pivot point on a lever arm and it produces torque. How much force would have to be applied to produce the same amount of torque if it were applied 1m from the pivot point? Assume that both forces are applied perpendicularly to the lever arm. a. same as the initial force b. one-third the intial force c. three times the initial force d. one-ninth the intiial force e. nine times the initial force 3
18. Consider the hoop in this figure; it rotates about point C. What is the magnitude of the angular acceleration of the hoop? 20. A block of unknown density is floating in a fluid such as in this figure. Which of these statements about the density of the block is true? a. 15 rad/s 2 b. 30 rad/s 2 c. 45 rad/s 2 d. 60 rad/s 2 e. 90 rad/s 2 19. You want to completely submerge a block of ice with mass=0.50 kg in liquid water. What force must you exert on the block in order to do so? a. the block has more mass than the fluid b. the block is more dense than the fluid c. the block has the same density than the fluid d. the block is less dense than the fluid 21. Water flows through a pipe. The pressure is 2000 Pa, and the water flows at 1.0 m/s. The water enters a narrower pipe, and the speed is 2.0 m/s. What is the pressure in this second section of pipe? a. 0.50 N b. 9.3 N c. 3.7 N d. 5.0 N e. 8.2 N a. 500 Pa b. 2500 Pa c. 5000 Pa d. 8000 Pa 22. A swift wind blows across the top of a chimney. What happens to the smoke rising inside of the chimney? a. the smoke rises more quickly b. the smoke is pushed down the chimney c. the smoke is unaffected by the wind 4
23. Which fills a larger volume: 100 kg of gold or 100 kg of lead? a. gold b. lead c. both have the same volume d. there is not enough information 26. Consider this manometer. Which statement best describes the relationship between P and P 0? 24. This figure shows a hydraulic lift. The force F 1 has a magnitude of 100N, and the area A 1 is 0.01m 2. If the area A 2 is 1.0m 2, what is the weight of the truck? a. P>P 0 b. P=P 0 c. P<P 0 d. it depends on the density of the material in the manometer a. 1000 N b. 10,000 N c. 100,000 N d. 1,000,000 N 25. A cylindrical container is 4.0 m tall and has a diameter of 2.0 m. It contains 200.0 kg of water; the container is not full. What pressure is exerted on the bottom of the container by the water? 27. Which of these states of matter is/are compressible? I. Solid II. Liquid III. Gas a. II & III b. I & II c. III only d. all of these are compressible 28. Who s awesome? a. The guy next to me. b. The lady in front of me. c. The fellow on my right. d. All of these!!!! a. 40,000 Pa b. 640 Pa c. 160 Pa d. 100,000 Pa 5
ID: A Exam 4--PHYS 101--Fall 2018 Answer Section MULTIPLE CHOICE 1. ANS: B PTS: 1 2. ANS: C PTS: 1 REF: F18 3. ANS: D PTS: 1 REF: F18 4. ANS: D PTS: 1 REF: F18 5. ANS: D PTS: 1 REF: F18 6. ANS: D PTS: 1 REF: F18-Tutor 7. ANS: C PTS: 1 REF: F18-Tutor 8. ANS: A PTS: 1 REF: F18-Tutor 9. ANS: B PTS: 1 REF: F15, F18 10. ANS: C PTS: 1 REF: F18 11. ANS: A PTS: 1 REF: F18 12. ANS: C PTS: 1 REF: F18 13. ANS: D PTS: 1 REF: F18 14. ANS: E PTS: 1 REF: F18 15. ANS: C PTS: 1 REF: F18--Tutor 16. ANS: E PTS: 1 REF: F18 17. ANS: C PTS: 1 REF: F18 18. ANS: A PTS: 1 REF: F18 19. ANS: A PTS: 1 REF: F18-Tutor 20. ANS: D PTS: 1 REF: F18 21. ANS: A PTS: 1 REF: F15, F18 22. ANS: A PTS: 1 REF: F15, F18 23. ANS: B PTS: 1 REF: F15, F18 24. ANS: B PTS: 1 REF: F18-Tutor 25. ANS: B PTS: 1 REF: F18-Tutor 26. ANS: C PTS: 1 REF: F18 27. ANS: C PTS: 1 REF: F18 28. ANS: D PTS: 1 1